1. Field of the Invention
The present invention relates to an electric wave-based intrusion detection system, in which leakage transfer passages for transmitting and receiving an electric wave are disposed in an area subject to monitoring an intrusion or a boundary thereof so as to monitor an intrusion of a person or other objects which should be monitored into the area subject to monitoring an intrusion or the boundary thereof using an electric wave, and a sensor device thereof.
2. Background Art
In an electric wave-based intrusion detection system according to the related art, a sensor device outputs a reference spectrum diffusion signal generated from a reference clock signal through a transmission leakage transfer passage. The sensor device correlates a spectrum diffusion signal received by a reception leakage transfer passage with the reference spectrum diffusion signal having a delay corresponding to a measurement distance of an intruding object to obtain a correlation signal. The sensor device detects the intruding object when a fluctuation in the signal level of the correlation signal is equal to or larger than a preset value (See JP-A-2004-306909 (FIGS. 1 to 3 and description thereof) and JP-A-2007-179401 (FIG. 4 and description thereof)).
When an intrusion of a person or other objects which should be monitored into an intrusion monitoring area or a boundary thereof is monitored using plural sets of intruder detection systems, the intruder detection system according to the related art has the following problem. That is, there is a case where both a spectrum diffusion signal output from a transmission leakage transfer passage of one intruder detection system and a spectrum diffusion signal transmitted from a transmission leakage transfer passage of another nearby intruder detection system are received by a reception leakage transfer passage. In such a case, a mutual interference may take place between the received spectrum diffusion signals, thus causing a detection error. However, in the process of developing the present invention, the present inventors have found that the detection error can be eliminated by separating the transmission leakage transfer passage of one intruder detection system from the reception leakage transfer passage of another nearby intruder detection system. Nevertheless, although the detection error can be eliminated by separating the transmission leakage transfer passage of one intruder detection system from the reception leakage transfer passage of another nearby intruder detection system, it was also found that an area in which it is difficult to detect an intrusion of an object which should be monitored is formed.
For example, as shown in FIG. 16, in order to prevent the detection error, when a separation distance of d is provided between the respective starting ends of a transmission leakage transfer passage 13a and a reception leakage transfer passage 15a connected to a sensor device 21a and the respective starting ends of a transmission leakage transfer passage 13b and a reception leakage transfer passage 15b connected to a sensor device 21b, a non-detectable area NDA is formed between both starting ends. Similarly, when a separation distance of d is provided between the respective terminating ends of the transmission leakage transfer passage 13a and the reception leakage transfer passage 15a connected to the sensor device 21a and the respective terminating ends of the transmission leakage transfer passage 13b and the reception leakage transfer passage 15b connected to the sensor device 21b, a non-detectable area NDA is formed between both terminating ends. Therefore, there is a problem in that it is difficult to prevent an intrusion of an object which should be monitored into an intrusion monitoring area from the non-detectable area NDA between both starting ends and the non-detectable area NDA between both terminating ends as indicated by empty arrows.
The interference is remarkable when the signal interval of the spectrum diffusion signal output from the transmission leakage transfer passage of one intruder detection system is the same as the signal interval of the spectrum diffusion signal transmitted from the transmission leakage transfer passage of another nearby intruder detection system. Furthermore, the interference also occurs even when the signal intervals of both spectrum diffusion signals are different from each other.